1. Field of the Invention
The present invention relates to a monitor for determining concentration of dissolved carbon dioxide (CO.sub.2) in a fluid sample stream, and more particularly, to a rugged device for continuous online monitoring of dissolved CO.sub.2 impurities in steam cycle water used for electrical power generation with both nuclear and fossil fuel steam generation systems.
2. Description of the Related Art
Dissolved carbon dioxide has been recognized as a potent cracking agent in basic solutions and a promoter of general corrosion in acidic solutions for many decades. However, no known on-line monitor exists which provides both high sensitivity and long term reliability. For example, U.S. Pat. No. 4,003,705 to Buzza et al. is directed to a device capable of detecting CO.sub.2 concentration with high selectivity by using a sample in a reaction which releases CO.sub.2 that in turn is reacted with an electrolyte. The change in pH of the electrolyte is indicative of the amount of CO.sub.2 in the sample. The device taught by Buzza et al. is very complex and not particularly sensitive, making it inappropriate for continuous monitoring of high purity water.
Single column ion chromatography is used for carbon dioxide detection in a device taught by U.S. Pat. No. 4,272,246 to Fritz et al. An anion exchange bed and an eluent of a very low electrical conductance organic salt solution, such as a solution of potassium phthalate, precedes a conductivity cell in the device taught by Fritz et al. This device is capable of detecting trace amounts of CO.sub.2 in high purity water; however, the construction and operation of the device taught by Fritz et al. is fairly complex and therefore unsuitable for continuous online monitoring in an industrial environment.
Ion chromatography is also used in a continuous system disclosed in U.S. Pat. No. 4,472,354 to Passell et al. which recommends the use of ion chromatograph exclusion for detection of carbonates. While ion chromotography is quite sensitive and it is possible, as taught by Passell et al., to use ion chromatography in a continuous monitor, it is desirable to have a simpler, more rugged CO.sub.2 detector with sufficient sensitivity to detect CO.sub.2 in the amounts found in the power generation loops of a pressurized light water nuclear reactor or fossil power plants.